How to create a good glass reflection with Principled BSDF
Honestly, for this I would just use a mix of a Transmission shader and a Glossy shader. But if you want to use a Principled shader:


Set the base color to #FFFFFF, so you don't have darkened glass. (Unless you want darkened glass, of course.)
Set the Transmission to 1 and the Transmission Roughness to 0.
Set the Specular to 0, you don't need it.
Set the Metallic to 0.2 or so. This will control how strong the reflections are; you should probably adjust it to fit your specific light source.
Set the IOR to 1.0, since you're making a cabinet—refraction will just slow things down.


Here's a quick test render:


(I got the HDR from here.)

As you can see, the icosphere is a reflection, the cube is not.